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排序方式: 共有1307条查询结果,搜索用时 15 毫秒
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George G. Laties 《Physiologia plantarum》1987,69(2):305-312
When treated with ethylene in O2, conditioned potato (Solanum tuberosum L. cv. Russet Burbank) tubers – that is, tubers kept at room temperature for 10 days or more – yield slices that are CN? resistant. Ten % CO2 in the gas mixture not only synergizes the effect of ethylene, but replaces the need for conditioning as well. The response to CO2 is more pronounced with increasing time from harvest. By contrast fresh slices from untreated tubers are CN? sensitive, as are slices from tubers incubated in O2 or O2 plus CO2. The suggestion is made that CN? resistance is constitutive, and that treatment with ethylene/CO2 in O2 confers on potato tuber tissue a resistance to the extensive degradation of membrane phospholipids that normally attends slicing and leads to the loss of CN? resistance. In this connection respiration inhibition by imidazole, an inhibitor of fatty acid α-oxidation, is extensive in slices of untreated tubers, and sharply diminished in slices of ethylene-treated tubers in proportion to their CN? resistance. The coextensive rise of respiration rate and CN? resistance in aged potato slices has led to the presumption that the CN?-resistant path mediates the respiration climax. Accordingly the alkaloid, lycorine, has been considered to inhibit the development of CN? resistance in aging potato slices because it curtails the wound-induced respiration. A comparison was carried out on the effect of lycorine on CN?-sensitive and CN?-resistant fresh slices – the latter obtained from ethylene/CO2-treated tubers. Lycorine suppressed the development of the wound-induced respiration without restricting the development of CN? resistance. 相似文献
6.
Claudio Orizio Renza Perini Arsenio Veicsteinas 《European journal of applied physiology and occupational physiology》1989,58(5):528-533
The contracting muscle generates a low frequency sound detectable at the belly surface, ranging from 11 to 40 Hz. To study the relationship between the muscular sound and the intensity of the contraction a sound myogram (SMG) was recorded by a contact sensor from the biceps brachii of seven young healthy males performing 4-s isometric contractions from 10% to 100% of the maximal voluntary contraction (MVC), in 10% steps. Simultaneously, the electromyogram (EMG) was recorded as an index of muscle activity. SMG and EMG were integrated by conventional methods (iSMG and iEMG). The relationship between iSMG and iEMG vs MVC% is described by parabolic functions up to 80% and 100% MVC respectively. Beyond 80% MVC the iSMG decreases, being about half of its maximal value at 100% MVC. Our results indicate that the motor unit recruitment and firing rate affect the iSMG and iEMG in the same way up to 80% MVC. From 80% to 100% MVC the high motor units' discharge rate and the muscular stiffness together limit the pressure waves generated by the dimensional changes of the active fibres. The muscular sound seems to reflect the intramuscular visco-elastic characteristics and the motor unit activation pattern of a contracting muscle. 相似文献
7.
L. Hove-Madsen H. Gesser 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1989,159(1):61-69
Summary Isolated heart ventricular preparations from rainbow trout were electrically stimulated to contraction. Following a temporary change in stimulation rate from 0.2 Hz to a higher value, the force fell to a minimum after which it increased and levelled off. Upon the return to 0.2 Hz a further transient increase in force appeared. The latter two responses were stimulated by an increased extracellular K+, which is known to inactivate the Na+ channel. The initial negative inotropic effect, in contrast to the two subsequent positive effects, was associated with a parallel decrease in amplitude of the action potential measured in 15 mM K+, used as an index of the Ca2+ influx. One micromolar (1 M) ryanodine did not affect either the negative or the positive responses due to an increase in stimulation rate, but depressed the force developed after prolonged periods of rest. Ten micromolar (10 M) adrenaline strongly inhibited the positive effects of an elevation of frequency. An elevation of extracellular Na+ from 141 to 166 mM had a similar effect. In conclusion, the positive effects occurring in 15 mM K+ do not seem to depend on the initial Na+ current. They may nevertheless depend on changes of the cellular Na+ balance as suggested by the effects of adrenaline, K+ and Na+. The functional role of the sarcoplasmic reticulum is unclear. 相似文献
8.
Pekka Oja Raija M. T. Laukkanen T. Katriina Kukkonen-Harjula Ilkka M. Vuori Matti E. Pasanen Seppo P. T. Niittym?ki Tiina Solakivi 《European journal of applied physiology and occupational physiology》1991,62(6):400-404
Two experiments were carried out to compare the cardiorespiratory and metabolic effects of cross-country skiing and running training during two successive winters. Forty-year-old men were randomly assigned into skiing (n = 15 in study 1, n = 16 in study 2), running (n = 16 in study 1 and n = 16 in study 2) and control (n = 17 in study 1 and n = 16 in study 2) groups. Three subjects dropped out of the programme. The training lasted 9-10 weeks with 40-min exercise sessions three times each week. The training intensity was controlled at 75%-85% of the maximal oxygen consumption (VO2max) using portable heart rate metres and the mean heart rate was 156-157 beats.min-1 in the training groups. In the pooled data of the two studies the mean increase in the VO2max (in ml.min-1.kg-1) on a cycle ergometer was 17% for the skiing group, 13% for the running group and 2% for the control group. The increase in VO2max was highly significant in the combined exercise group compared to the control group but did not differ significantly between the skiing and running groups. The fasting serum concentrations of lipoproteins and insulin did not change significantly in any of the groups. These results suggested that training by cross-country skiing and running of the same duration and intensity at each session for 9-10 weeks improved equally the cardiorespiratory fitness of untrained middle-aged men. 相似文献
9.
Gary J. Rose James G. Canfield 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,168(4):461-467
Several species of weakly electric fish reflexively change their frequency of electric organ discharge (EOD) in response to sensing signals of similar frequency from conspecifics; that is, they exhibit jamming avoidance responses (JAR).Eigenmannia increases its EOD frequency if jammed by a signal of lower frequency and decreases its EOD frequency if jammed by a signal of higher frequency. This discrimination is based on an analysis of the patterns of amplitude modulations and phase differences resulting from signal interference. Fish of the closely related genus,Sternopygus, however, do not exhibit a JAR. Here we show that despite lacking this behavior,Sternopygus shares many sensory processing capacities withEigenmannia:
相似文献
1. | Fish could be conditioned to discriminate the sign of the frequency difference (Df) between an exogenous sinusoidal signal and its own EODs with as few as 300 training trials. |
2. | Fish can discriminate the sign of Df for jamming signals with an amplitude as low as 2 V/cm (p-p); which is approximately 40 dB below the amplitude of the fish's EOD, as measured lateral to the operculum. |
3. | Fish appear to discriminate the sign of Df by evaluating modulations in signal amplitude and differences in the timing of signals received by different areas of the body surface. |
4. | Sternopygus processes electrosensory information through band-pass modulation filters. Tuning to modulation rates over at least 4–16 Hz exists. |
10.
James R. Anderson Catherine Fritsch Bernadette Favre 《Primates; journal of primatology》1990,31(4):611-615
An adult femaleLemur catta and an adult femaleEulemur fulvus were given edible rewards for scratching. Both subjects learned to scratch in order to obtain the rewards, showed diminished
rates of scratching during periods of extinction, and learned to scratch preferentially with one foot when required. TheLemur catta subject was more responsive to the changing experimental conditions than theEulemur fulvus. The conditionability of scratching in primates does not appear to be directly related to the widespread occurrence of scratching
in simian social contexts. 相似文献